Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts constructed of biocompatible materials have been employed to replace or bypass damaged or occluded natural blood vessels. In general, endovascular grafts typically include a graft anchoring component that operates to hold a tubular graft component of a suitable graft material in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in situ to anchor the tubular graft component to the wall of a blood vessel or anatomical conduit. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the opposition forces provided by the radially expandable stents.
Grafting procedures are also known for treating aneurysms. Aneurysms result from weak, thinned blood vessel walls that “balloon” or expand due to aging, disease and/or blood pressure in the vessel. Consequently, aneurysmal vessels have a potential to rupture, causing internal bleeding and potentially life threatening conditions. Grafts are often used to isolate aneurysms or other blood vessel abnormalities from normal blood pressure, reducing pressure on the weakened vessel wall and reducing the chance of vessel rupture. As such, a tubular endovascular graft may be placed within the aneurysmal blood vessel to create a new flow path and an artificial flow conduit through the aneurysm, thereby reducing if not nearly eliminating the exertion of blood pressure on the aneurysm.
In general, rather than performing an open surgical procedure to implant a bypass graft that may be traumatic and invasive, endovascular grafts which may be referred to as stent-grafts are preferably deployed through a less invasive intraluminal delivery procedure. More particularly, a lumen or vasculature is accessed percutaneously at a convenient and less traumatic entry point, and the stent-graft is routed through the vasculature to the site where the prosthesis is to be deployed. Intraluminal deployment is typically effected using a delivery catheter with coaxial inner and outer tubes arranged for relative axial movement. For example, a self-expanding stent-graft may be compressed and disposed within the distal end of an outer catheter tube distal of a stop fixed to the inner member. The catheter is then maneuvered, typically routed through a body lumen until the end of the catheter and the stent-graft are positioned at the intended treatment site. The stop on the inner member is then held stationary while the outer tube of the delivery catheter is withdrawn. The stop prevents the stent-graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent-graft is released from the confines of the sheath and radially self-expands so that at least a portion of it contacts and substantially conforms to a portion of the surrounding interior of the lumen, e.g., the blood vessel wall or anatomical conduit.
In recent years, to improve optimal control and alignment during deployment and positioning of a stent-graft, various tip capture spindles have been incorporated into the delivery system utilized for percutaneously delivering the stent-graft prosthesis. Tip capture involves restraining the proximal end stent of the stent-graft in a radially compressed configuration in conjunction with the main body restraint achieved by other delivery system components, such as a tubular cover shaft or sheath. The tip capture spindle can be activated at any time during stent-graft deployment to suit any number of system characteristics driven by the therapy type, stent-graft type, or specific anatomical conditions that may prescribe the release timing. Typically, the tip capture release is activated after some or all the main stent-graft body release, and thus provides a mean of restraining the stent-graft during positioning and any re-positioning. Additional restraint of the stent-graft is a key characteristic when the operator is attempting to accurately position the stent relative to an anatomical target. The tip capture restraint also aids in reducing an abrupt force of expansion when the stent-graft is released from the graft cover or sheath.
A stent-graft may be tightly compressed within a catheter for delivery, imposing high levels of friction between the stent-graft and the outer sheath of the catheter. Thus, a delivery system must be capable of imparting a significant, yet controlled, force to retract the outer sheath and deploy the stent-graft. A need in the art still exists for an improved delivery system having a handle that consistently and reliably retracts the outer sheath thereof in order to deploy a prosthesis in a body lumen.